A fuel cell has been proposed as a clean, efficient and environmentally responsible power source for electric vehicles and various other applications. In particular, the fuel cell has been identified as a potential alternative for the traditional internal-combustion engine used in modern vehicles.
One type of fuel cell is known as a proton exchange membrane (PEM) fuel cell. The PEM fuel cell typically includes three basic components: a cathode, an anode, and an electrolyte membrane. The cathode and anode typically include a finely divided catalyst, such as platinum, supported on carbon particles and mixed with an ionomer. The electrolyte membrane is sandwiched between the cathode and the anode to form a membrane-electrolyte-assembly (MEA). The MEA is often disposed between porous diffusion media (DM) which facilitate a delivery of gaseous reactants, typically hydrogen and oxygen from air, for an electrochemical fuel cell reaction.
As described in U.S. Pat. No. 6,127,058, individual fuel cells may be aligned in a planar array that is electrically connected via interconnect tabs. In U.S. Pat. Nos. 6,080,503 and 6,495,278, electrochemical fuel cell stacks having adhesively bonded layers formed for individual fuel cell modules are also described. PEM-type fuel cell assemblies having multiple parallel fuel cell substacks that employ shared fluid plate assemblies and shared membrane electrode assemblies are also disclosed in U.S. Pat. No. 5,945,232.
In automotive applications, individual fuel cells are often stacked together in series to form a fuel cell stack with a voltage sufficient to provide power to an electric vehicle. Connecting individual fuel cells in series requires the fabrication and handling of a multitude of individual fuel cells, however. A height of the resultant fuel cell stack having the multitude of individual fuel cells may limit placement of the fuel cell stack within an electric vehicle. Furthermore, DC-to-DC voltage converters are typically employed in fuel cell systems to enable the fuel cell stack to achieve the sufficient voltage. Voltage converters and related componentry add undesirable complexity to the fuel cell system.
There is a continuing need for a simplified fuel cell assembly which militates against the need for DC-to-DC converters, the need to fabricate a multitude of individual fuel cells, and facilitates a placement of the fuel cell assembly within a vehicle.